1. Field of the Invention
This invention relates to a ball-shooting game machine such as a pachinko game machine and, more specifically, to a ball-shooting game machine, in which game balls shot from a ball shooter to a game zone over a game board are detected and the game controlled according to the number of detected shot balls.
2. Description of the Prior Art
In a pachinko game machine, a ball shooter is provided for shooting game balls onto a game board surface, having one or more winning holes or other winning devices, and a plurality of nails or pins which interfere with and guide the balls' travel. The object of the game is to get the balls to enter a winning hole or other winning device. It is well known that the probability of producing winning balls; i.e., getting balls to enter winning holes is varied depending on the position, orientation, and angle of nails or pins arranged on the game board surface, as well as the interval between adjacent nails. For the pachinko shot, therefore, the adjustment of nails is an important operation. For the player, on the other hand, it is most important to find a pachinko game machine which has been adjusted to provide a higher probability of producing winning balls.
The adjustment of the orientation, interval, and the like of nails to adjust the probability of producing winning balls, however, requires a very subtle operation involving units of measure as small as 0.01 millimeter, and further requiring experts having sophisticated skill for making adjustments.
Devices have been proposed for adjusting the probability of producing winning balls in a pachinko game machine through automatic nail adjustment. For example:
(1) Japanese Patent Publication No. 59-35633 discloses a device in which the interval between a pair of nails above a winning hole can be varied in a predetermined range; and
(2) Japanese Patent Publication No. 61-36949 discloses a device in which the position or inclination of nails associated with each winning hole is varied according to the winning probability of each winning hole.
Techniques are also known for controlling the winning probability without nail adjustment but rather by setting the open-time of a so-called tulip or variable winning device. Examples of these techniques are:
(3) Japanese Patent Publication No. 54-78233 which discloses a device to control the open time of winning device such that the gain index can be set to be in a predetermined range by the pachinko shop; and
(4) Japanese Patent Publication No. 61-47548 which discloses a device to designate the open time of winning device according to a random number electronically generated in response to detection of a winning ball.
In the devices (1) and (2) noted above for performing nail adjustment, however, it is necessary to effect subtle adjustment with a high degree of accuracy. Therefore, the adjustment mechanism must be precise and is inevitably expensive, so that it is difficult to adopt such a mechanism to replace the conventional manual adjustment in current machines.
In addition, with the devices (3) and (4) noted above for setting the open time of variable winning devices, it is difficult to permit variable setting of winning probability through fine adjustment like the nail adjustment.
Further, with a pachinko game machine which is subtly adjusted in the manner as described above, the production of winning balls depends to a great extent on the skill of the player. Therefore, it is difficult to obtain winning balls unless the player is highly skilled or a professional. The prior art games, therefore, lack impartiality as a game designed for the unskilled general public.